Liquid solids separation apparatus



Aug 20, 1946 Y E. A. PACKARD 42,406,212;

LIQUID SOLIDS SEPARATION APPARATUS l @riginal Filed Feb. 14, 1942 6Slxeets-SheeiI 1 A 20, 1946 E. A. PACKARD 2,406,248

LIQUID SOLIDS SEPARATION APPARATUS Original Filed Feb. 14, 1942 6Sheets-Sheet 2 Aug. 20, l946 r E. A. PACKARD LIQUID SOLIDS SEPARATIONAPPARATUS e sheets-snee; s'

Original Filed Feb. 14. 1942 INVENTOR Aug. 20, 1946. 5A. PACKARD2,406,248

'LIQUID SOLIDS SEPARATION APPARATUS Original Filed Feb. 14, 1942 6Shyets-Sheet 4 INVENTOR Aug. 20, 1946. E.A. PACKARD LIQUIDSOLIDSSEPARATION APPARATUS Original Filed Feb.- 14, 1942 6 Sheets-Sheet5 www l. In. V

6 Sheets-Sheet 6 E. A. PACKARD l LIQUID soLIDs SEPARATION APPARATUSOriginal Filed Feb. 14, 1942 l- ZL 1 mmm Ohh Aug. 2o, 1946. f

' INVENTOR www www Patented Aug. 20, 1946 LIQUD SOLIDS SEPARATIONAPPARATUS Edwin A. Packard, Ynkers,N. Y. substituted for abandonedapplication Serial No.

430,972, February 14, 1942.

This appiication December 3, 1943, Serial No. 512,684

28 Claims.

The invention relates to the separating of solid particles from theliquid of a suspension in which they are carried.

Many types of suspended matter can be caused to float on the top ofliquid containing the same when such liquid suspension is transferredfrom a locality whereat it was exposed to normal atmospheric pressure toa closed container wherein it is combinedA with liquid undergoingtreatment in the container and exposed to overlying air or other gaswhich is continued at pressure substantially subatmospheric.

The invention hereof has in view as a broad aspect thereof a novelprocess, and a novel apparatus for performing the process, according towhich there is involved the exposing of a confined continually fedever-changing body of such liquid suspension to overlying gas maintainedat pressures substantially sub-atmospheric whereby the suspended .solidsreadily rise as a oat, scum, or froth, on the surface of the liquid, thetransferring and delivering of a controlled quantity of scum or froth asan overiiow float-fraction leaving the confined body along one path, andthe upwardly-transferring, overflowing and ultimate releasing of acontrolled quantity of clarified liquid as an outilowing liquid-fractionalonga second path, namely, along a path leading from a lower orintermediate portion of the confined body.

rIhe invention, according to a more specific aspect thereof, extendsinto a situation 'wherein there is provided within or for the lowerportion of said confined body a zone of relative quiescence favorable tothe settling of heavy solids as a sediment and to the collecting andprogressively transferring of said sediment as a heavy solid fractionalong a third path, namely, along a third path leading from thelowermost portion of said confined body. In the instance of this morespecic aspect of the invention, the reduction in pressure of thesub-atmospheric pressureV gas is not sufficient for the effects thereofto reach, or extend downwardly into the quiescent lower zone therebyavoiding any functional influence of the reduced pressure gas on theliquid in that zone and more specifically avoiding turbulent conditionswhich might otherwise exist if the functional effects of the vacuum orreduced pressure reached down into said lower zone.

Important phases or aspects of the invention revolve about the featuresof construction of a novel closed tank or .vacuum type of unit intowhich the liquid suspension is continually fed to a confinedever-changing body of such liquid suspension that is overlain andexposed to gas at substantially sub-atmospheric pressures, within whichtank there is a transfer of a controlled quantity of froth, scum orother float material-herein broadly referred to as scumfrom the top ofthe liquid body and a Adelivery of the transferred scum as aoat-fraction to a locality outside of the tank without permitting theentrance of outside air into the tank, an upward transfer of clarifiedliquid from a lower or intermediate portion of said body to and past ahigh section or overflow weir which in effect regulates the relativequantity of overflow clarified liquid as compared with the scum transferheretofore referred to and the subsequent 1delivery of overflowedclarified liquid to a locality outside of the tank without permittingthe entrance of outside air into the tank.

According to a more specic phase or aspect of the invention, it extendsto such a closed tank or vacuum type of unit in which provision is madefor a quiescent sedimentation section within the lowermost portion ofthe tank and for such unit there is also provided means for collectingand transferring sedimented solids as a third fraction from the lowerinterior portion of the tank without permitting the entrance of air intothe tank and in a manner to effect such transfer of the third fractionwithout substantially eifecting the general level of the liquid withinthe tank.

The different features and aspects of the invention will be manifest andmore fully appreciated from the following portion of the specication andfthe accompanying drawings which constitute a part of the specification.

In the drawings: i

Fig. 1 is a, plan view partly in section, and Fig. 2 is a vertical view,mostly in section, of one form of apparatus.

Fig. 3 is a partial horizontal sectional view taken as on the horizontalplanes indicated by the broken line 3 3 of Fig. 2 looking in thedirection of the arrows.

Fig. 4 is a plan view, partly in section, and Fig. 5 is a vertical view,mostly in section, of another form of apparatus.

Fig. 6 is a horizontal sectional View taken as on the horizontal planesindicated by the broken line 6 9 of Fig. 5 looking in the direction ofthe arrows.

Fig. 7 is a horizontal View, some in plan and some in horizontal sectionof another form of the apparatus.

Fig. '7a is in reality a part of the horizontal View of Fig. 7. butsince it may appear to be detached from Fig. '7, it has been designatedas Fig. 7a.

Fig. 8 is a vertical view, mostly in section, of the apparatus of Fig.'7.

Fig. 9 is a plan view, partially in section, of a portion of theapparatus shown in Figs. 'i and 8. Fig. l is a horizontal view,partially in section and partially broken away; it is a View taken as onthe horizontal planes indicated by the line i3- I3 of Fig. 8 looking inthe direction of the arrows. Figs. ll and 12 are respectively ahorizontal l0 Ving thereinto from a lower or intermediate porsectionaland a vertical View of a detail of the indicated by the line I I-I I inFigs. 8 and 12, and Fig. l2 being a vertical sectional view ytaken as.

on the line of I2|2 of Fig. 11 looking in the direction of the arrows.

Fig. I3 is a vertical sectional view of a detail of construction whichmaybe employed at and for the top of the tank shown in Fig. 8.

Fig. 14 is a horizontal sectional View taken as on the horizontal planesindicated `by the line ifi- I4 of Fig. 13 looking in the direction ofthe arrows. l

Fig. 15 is a vertical sectional detail View of a feature of constructionwhich can be employed in and for the'upper throat member of the tankshown in Fig. 8.

In the drawings like parts have been given like reference characters.Certain features or operative parts that are common to each of the formsillustrated will first be referred to.

Each form of apparatus includes or embodies as an associated partthereof a feed-receiving and initial treating basin I3, I IU or 2 I0; aclosed tank I I, III or 2 I I, providing a main separating compartmentwherein there is held an ever-changing body of liquid suspension that isimmediately overlain by and exposed to gas maintained at pressuressubstantially below that of the pressure of the atmosphere outside ofthe tank; a feeddelivery conduit in the form of a draft tube I2,

2 or 2 I2 leading from the basin and terminating in an upf-low dischargesection which submergedly delivers the incoming liquid suspension intosaid ever-changing liquid body; means providing a scum orfroth-receiving launder I3, I|3 or 2I3 4 having an overflow weir oroverpass transfer edge SW, ISW or 2SW over which floating scum passesfrom the top of said body into said launder; means for passing the scum,froth, or other oating material from the scum launder to a localityoutside of the tank without permitting the ingress of outside air intothe tank, namely, by scum outflow means provided by a downflow pipe orconduit in the form of a barometric leg I4, |14 or 2|4 the lower en'd ofwhich continuously dips into a body of scum or liquid within a lowscum-release box I5, I`I5 or 2I5, identifiable as a scum collector; anauxiliary tank or liquidheight control structure IB, IIS or 2I6providing a liquid-receiving and gas-holding compartment or space 22,|22 or 222 extending to elevation sub-- stantially higher than that andto elevation substantially lower than that of the scum-transfer Weir SW,ISW or 2SW; a pipe or other passageway providing means II, II'I or 2I'1for insuring constant communication between the upper interior portionof the auxiliary compartment 22, |22 or 222 and the upper interiorportion of the main tank I I, I II or 2| Iy whereby the pressure of thegas within the main tank and the pressure of 4 the gas Within theauxiliary compartment will always continue substantially alike, to wit,at like pressures always substantially less than that of the pressure ofthe air outside of the apparatus; pump means I8, II8 or ZIB forwithdrawing air or other gas from the gas-holding portions of said tankand the auxiliarystructure associated therewith and for therebymaintaining the pressure of the gas therein substantiallysub-atmospheric; means for receiving clarified liquid passtion of theliquid body, to wit, means in the form of apvbustle-collecting sectionI9, IIB or 2I9 located along an intermediate or lower portion of thetank I I, I i I or 2 I I; and clarified-liquid transferv means 20, |20or 220 embodying up-ilow pipes or conduits 2|, I2| or 22| leading fromthe bustle section upwardly to the lower interior portion of theauxiliary tank or liquid-height control structure I6, I I 6 or 2 I 6,means providing a high liquidfraction overflow weir or dam LO, ILO or2LO past which any outflowing clarified liquid must pass before deliveryas overflowed liquid into the chamber or compartment 22, I 22 or 222 ofthe auxiliary structure I3, |`|6 or 2|3, and a downflow pipe or conduit23, |23 or 223 in the form of a barometric leg extending from the lowerportion of said compartments downwardly toand into a low claried-liquidrelease box or tank 24, |24 or MII- identifiable as anefuent-receiver-holding a body or pool of clarified liquid into whichthe low end of the barometric leg constantly dips and by which it isliquid-sealed against the inflow of outside air. The intake end 4I, I4Ior 24| of the feed supply pipe or draft tube I2, I|2 or 2I'2 is insubmergence whereby it is always liquidsealed against the entrance ofoutside air therethrough into the tank I I, I II or 2| I. Because ofthis fact and also since the barometric leg sections already referred toare liquid-sealed, the structure of the apparatus is such that theseparation tank I'I, III or 2|I is constantly sealed against theentrance of outside air 'thereinto during the normal functioningthereof.

Feed. receiving basin 10, 110 or 210 Incoming liquid suspensions aredelivered by the pipe 33, or 233 into an initial feed-receiving section3|, I3I, or 23| of the basin I0, IIO, or ZIB, to wit, at a localitythereof in front of the partial partition 32, |32 or 232. The fedmaterial passes from this section 3 I', I3| or 23| through an underpassspace 33, |33 or 233 left below the partial partition 32, |32 or 232into a region whereat it comes under the operative influence of agas-diffusing member in the form of a rotatable impelling means 34, |34or 234. Air or other selected gas is supplied through a valve-controlledpipe 35, |35 or 235. Under the operative influence of this impellingmeans the air or other gas is intimately mixed and diffused within andthroughout the liquid passing saidv agitating or impelling means.

In the treating of certain liquid suspensions, it is advisable to add afrothing agent, flotation oil, or other chemical reagent and for suchpurpose there is indicated and provided a holder 36, |36 or 233. Avalve-controlled pipe 31, |31 or 231 is also indicated as means by whichthe contents of said holder 36, |36 or 236 may be delivered into theliquid suspension so as to come under the operative influence of theimpelling member 34, I 34 or 234 as it functions. A relatively largeregion is provided within the basin at 38, |38 or 238 to remain in theliquid suspension. In order to insure sufhcientretention for the. liquidinthe section 38, lror'` 238',` 'there is provided withinithe:-

basin an. upstanding. partition or dam 39,' Ifiror` 239 thetupper edge4.0, MB or240 of whichd'e'- termines the minimum level of the liquid. inthe basin. TheV surface levelI ofthe overiiowedV liquid in the receivingsection 43, L43 or 243 therefor is generally at elevation within a rangeincluding fan "elevation somewhat lowerthan -that o-f the overflow weiriii), I di) or'f240; and an elevation higher thanN the `intake end 41',I4] or 24| of thev draft. tube l2,l H2 or lZ'whereby the intake endofthe latter always continuesA in submergence. An adjustable gate dit,HitV orA 242 isk provided so asl to regulate the area of the entrance ofthe intake end di, i4! or 24! of the draft tube1 oreven to completelyshut off the intake opening thereof at the will of an operator. Fromthe, foregoing it will 'be noted that thel features of construction justdescribed with regard to the feed-receiving andinitial treating' basinsapply to each, form shown. i

The construction and functioning of the basin it), `I lil or 2li! hasbeen described in order that one may readily appreciate anypre-treatment operations on the liquid suspensions and the stepsemploye'dflrespecting the supplying of the same to the separation tankIl, Hl or 2H wherein the liquid suspensions are further treated andhandled in such manner as to obtain or eiect the removal of certainsuspended solids as froth, scum or other type of float fractioneach andall identiable as scum thus used herein as a, generic` term-which flowsoutwardly along one path involving its passage over the transfer weirSW,ISW or ZSW into the scum-receiving launder i3, H3 or 2| 3,"and theremoval of a claried liquid-fraction along another path involving` itspassage from a lower or intermediate portion of the-'tank upwardlytowards and past a high liquid-fraction overflow weir or dam LO, ILO orELO that regulates the minimum elevation for the surface,

level of the liquid maintained within the tank and its passage asoveriiowed effluent into chamber 22, |22 or 222' and thence downwardlythrough the liquid-sealed barometric leg. section before release totheatmosphere.

TankA of Figs. 1, Z and 3 Respecting. the tank unit ofthe form shown inFigs. 1, 2y and 3 it will vbe noted that this embodiesl an.rupwardly-extendingf marginal wall 115 circular in plan and a rising caporr top member itv connected Vto the upper edge portion of the marginalwall; shaped member t1 connected to the lower portion of the marginalwall, extending outwardly therefrom and disposed at elevation somewhathigher than that of the' lower edge 48 of the marginal wall whereby thememberflll constitutes the roof or top portion of the bustle section I9and whereby the lowermost portion 49 of the marginal wall provides aninner wall for the bustle sectionV I9; ran outer cylindrical; member 50extending downwardly from and connected to the outer edge of the annularkring member 41 whereby the cylindrical member 5l] constitutes the outerwallv of the bustle section I 9; and a dish-shaped or depressed Vbottommember 5l which is connected to the member 5I! whereby the member 5lprovides the lower defines for the bustle section I9 and also serves` t0provide a floor for the tank.

` Inv the `functioning of the apparatus some any annular ring--sedimentedi` material "may collect on: the bottom of rtliist'arrk and avalve-controlled discharge means 52: is. provided" for the release ordischarge of such sedimented material from the interior of the tank` ifand when it becomes advisable todo so incident to the normal operationof the apparatus.

It is Yclear from theA drawings and from that whichk has preceded howtheliquid can pass from the bustle section i9 upwardly into the pipesections or conduits 2l. In the construction of the form shown by saidFigs. 1, 2 and 3 and the overflow weir means providing theliquid-fraction overflow weir LO- is realized by vertically adjustableoverflow tips that surround the upper end portions of the conduits 2i.These overflow tips or weir members 25 vin effect become continuationsof or positionable members associated with the pipes or conduits 2l. Theadjustment thereof is effected through the medium of the rods 53 whichpass through the sealing means 5A, providing packing material at 55 andwhich rods are actuated through the medium of suitably supportedhandwheels which function as adjusting nuts 55 on the screw threadedportions 5l of the rods 53. The upflow conduit sections EI are three innumber as is apparent from Fig. 3. The intake ends 26 thereof aresymmetrically arranged: withV respect to the bustle section i?) of thetank Il and the upper outiiow ends thereof are symmetrically arrangedabout and with respect to the upper or intake end of the downow conduitor barometric leg 23.

The upper overow Weir edges of the tips or members 25 collectivelyconstitute or provid-i the liquid overflow weir LO which determines theminimum, and in effect the normal operative level for Vthe liquid withinthe tank. The elevation of each of these high liquid-fraction overflowweir members or tips 25 is generally somewhat lower than that of thetransfer-Weir edge SVI past which froth or scum must pass on its way tothe receiving launder i3 therefor. By effecting the desired adjustmentor elevation of these members 25 and thereby of the general elevationfor the liquid overow-weir edge LO` one is enabled to effect acontrolled split delivery of the clarified liquid-fraction as overflowmaterial past the high liquid-overflow weir LO and of the scum orfloat-fraction past the scum or float-transfer weir edge SW.

The pump means i8 is relied upon to maintain the vacuum or reducesatmospheric pressure conditions within the tank so that the reduction inpressure when compared with that ofthe atmosphere is by way of examplein theY tank l! must be sufficient whereby the atmos-` pheric pressureof the outside air onthe over flowed liquid suspension in the receivingsection blof the basin I!! is sufficient to effect or i force thetransfer, as feed delivered into the and the upward delivery from theupper ex-l panding end 63 of the rising upiiow section 52 of the drafttube into the ever changing body Y 7 of liquidv undergoing treatmentwithin the closed top or main tank II'. The upper-most or terminal edgeof the rising section 62 is at elevation lower than that of the overpasstransfer edge of scum Weir SW or of the overflow edge of liquid-overflowweir or effluent dam LO. The liquid thus passed inwardly through thedraft tube is submergedly delivered within the liquid-holding portion ofthe tank but at elevation substantially higher than that of the loweredge 48 of the marginal wall 45, or as otherwise defined, at anelevation substantially above that of the intake openings for the upilowpipes 2|.

It will be noted from that which has preceded that the body of liquidwithin the tank is maintained up to a level determined by theliquidoverilow weir LO and that above this general level there existsthe air or other gas which is maintained, within the tank and itsIassociated auxiliary chamber, at a sub-atmospheric pressure determinedvby the operating of the pump I8. This vacuum or reduction in pressureof the gas as compared with thatv of the outside air has on the body ofliquid suspension overlain thereby and exposed thereto a functionaleffect which is greatest in the uppermost portions of theV liquid, andthe effect thereof progressively decreases with respect to the liquid inthe lower levels. The vertical distance between the scumtransfer edge SWand the lower edge 48 of the marginal wall 45 is therefore preferablymade so that it approaches the height of the column of water whichindicates the pressure differential between the inside and outside ofthe tank. In other words7 for the pressure reduction mentioned, thevertical distance between either the scum-transfer Weir edge SW or ofthe liquidoverflow weir edge LO on the one hand and either the loweredge 48 or the entrance ends 25' of the conduits 2| on the other hand,would be in the neighborhood of 9 ft., possibly somewhat less, and theentrance or intake end 4I ofthe draft tube I2 should be at elevationsomewhat lower than that of the lower edge 48. The edge 48 roughlyindicates the upper limits of an assured region of relative quiescence.The portion of the tank extending downwardly below this vline may beviewed as providing a zone of relative quiescence favorable to thesettling of solids therein and it is from this general region that theclarified liquid is taken that is passed to discharge from the'bustlesection I9 to the exterior of the tank 'by means of the pipes 2 I, pastthe high-liquid overflow weirs LO and ultimately downwardly through thebarometric leg 23.

' 6I and a rising upflow section 62 terminating in an expanding deliverythroat 53. The delivery end of the draft tube has associated therewithan annular distributing plate 54 which is submergedly disposed withinthe liquid-holding portion of the tank II. This plate is at .elevationsomewhat lower thanV that of the scum transfer edge SW and at elevationsubstantially higher than that of the lower edge 43 of the marginal wall45. This plate E4 is connected to the throat portion E3 of the drafttube whereby in effect it becomes a horizontal extension or flange forsaid throat portion. This plate is of less diameter than that of theinterior of the marginal wall whereby an annular downflow passageway isleft at 65. Brackets .66 are secured to the marginal wall 45 forsupporting the plate 64 and thereby the inner or terminal end Yof thedraft tube I2. There is a liquid-tight connection at 61 between theoutside portion of the draft tube and that portion of the tank structurewhereat the draft tube passes from the exterior of the tank into thetank.

The inflow velocity of the liquid through the tube is sulcient to insurea delivery from the upper'end of the tube of any and all solid matterwhich may exist in the suspension supplied therethrough to the interiorof the tank Il but this velocity should not be sufficient to cause adegree of turbulence within the upper portion of the tank Kthat wouldprevent a proper splitting of the floating material as a float-fractionand the claried liquid as a clarified liquid-fraction.

For effective operation the distributing plate 64 may be disposed at anelevation, for example, one and one-half feet to two feet lower thanthat of the scum-transfer edge SW, but the elevation selected may varyaccording to the type of liquid suspension treated, the type ofScum-fraction or split off desired, or the degree of vacuum or reducedpressure employed for the gas overlying the ever-changing liquid onlywithin the tank Il.

The inflowing suspension is preferably Vdetained over thedistributingplate a sufficient time whereby there is an effective risingof the floatl able material to the top of the liquid body as a Whole asthe operative influence of the reduced pressure gas within the upperportion of the tank is most effective upon the uppermost portionY of theliquid body. This horizontal plate 64 also leads to a more quiescentcondition of the liquid immediately underlying the same by compelling arealization of a major effect of the reduced gas pressure on thatportion of the supplied liquidl suspension while the latter is intransit over and along the upper surface of said plate 64.

Reference has heretofore been made to the barometric leg or conduitsection 23 by which overflowed clarified liquid is passed into the lowclarified-liquid release tank or box 24. An inspection of Figs. 1 and 3will show that this barometric leg 23.has been shaped so that the lowtank or box 24 into which it extends is, in plan, located at one side ofthe draft tube I2 whereby the barometrc leg can pass downwardly by thedraft tube. The low tank 24 is in the form of an open box or tube and abody or pool of sealing liquid 68 is maintained therein up to a, minimumelevation by a dam 69 having for the overflowV member thereof a weirmember 'Ill which is adjustable as to height through the medium of a rodll having a threaded upper end 'I2 and an associated handwheel or nut'I3 which is suitably supported from and with respect to the tank or box24. The lower discharge end of the barometric leg constantly dips intothe body or pool of sealing liquid 68. The claried liquid flowing intosaid pool or body of sealing liquid is ultimately released over saidweir member 10 and ultimately flows from the box as through any suitableoutflow means 14. Because of this functioning ofthe structure described,this. box or tank and its associated parts is sometimes herein referredto as a liquid-fraction release box having a low liquid release weir l0.This box or tank is also sometimes referred to as an eflluent receiver.

The description hereby given with respect to this claried liquid-releasebox substantially applies to the similar construction in the form ofeach of the other gures.

As to the barometric scum-discharge leg I4 and the release box I5 intowhich it extends, it will be noted that a body or pool 'I6 of sealingliquid is maintained therein because of a dam structure 'i which can bepositioned as to overiiow elevation by removable or replaceable overiiowboards T8. Tins body or 4pool of liquid I6 may be provided by liquidinitially supplied thereto as a sealing medium for the discharge end ofthe barometric leg which dips into the same. Such sealing body or poolwill be maintained because there will always exist more or less liquidwhich passes the scum weir or transfer edge SW with the floatingmaterial that passes into the scum-receiving launder I3. The overiiowedor release scum which passes the Weir edge provided by the upper board18 is ultimately passed for the desired disposition by any suitablemeans as for example by a conduit or pipe 1S. This overflow box or tanktypifies the overflow box or scum release means as shown in'the otherforms herein illustrated and is sometimes referred to as a scum orfloat-fraction release box having a low scum-release weir 11. It is-alsosometimes referred to herein as a scum collector.

The description hereby given with respect to the scum collector oroat-fraction release box having a low scum release weir substantiallyapplies to the similar construction in the form of each of the othergures.

Apparatus of Figures 4, 5 and 6 ln the main the features of constructionof this apparatus correspond to the apparatus of Figs. l to 3 inclusivealready described.

In the tank III of this second form there is the upwardly extendingmarginal wall |45 which is circular in horizontal cross section. At thelower portion of this wall there is the structure providing the bustlesection IIS and the dishshaped or depressed member ISI providing thebottom of the tank. The closure top for the tank is provided by anupwardly and inwardly-extending roof member I8| and an invertedcupshaped member |84. The roof member IBI in shape resembles the surfaceof a frustrum of a cone and terminates in an upwardly-extendingcylindrical throat portion |82 that provides an upow opening the centerof which is concentric with the marginal wall |115. The lower edge ofthis roof member has a gas-tight connection to the upper edge of themarginal wall |45. In the construction shown there is associated withthe -xed cylindrical throat portion |82 a vertically-adjustable Weir,ring, or cylindrical member |83 of which the upper or overpass transferedge portion provides the horizontally-extending scum overflow weir ISW.The means by which this Weir member |83 is supported and verticallyadjusted will later be described.

In order to complete the capping or top csure for the tank there isemployed the inverted cup-shaped member |84 embodying a top or uppermostportion and a downwardly-extending flange or rim portion |85` which iscircular in horizontal cross-section but which is assembled in positionso that it is eccentric or off center with respect to the cylindricalthroat portion |82. The eccentrically-disposed rim portion |86 of thegas-tight top or capping member |84 is connected to the roof member I8Iwhereby the gastight closure for the top of the tank is completed andwhereby there is also provided the scum-receiving trough or launder I I3that progressively increases in depth and cross-sectional area as itapproaches the passageway |81 leading into that portion of thescum-discharge structure which includes the barometric leg IM,

With respec-t to the scum-discharge structure illustrated in this'ligure it will be noted that it embodies a hollow casing l|88 that isconnected to the tank I I I so asto be in communication with the scumAWeir H8 through the 4medium of a pipe |84 that provides theaforementioned passageway |87. The yhollow casing |88 is made up of ahollow body member `I 8S and a cover member IBG. Itv also has atransverse baie ISI Yextending downwardly from the cover member |88.rIhe lower end of the baille terminates at elevation substantially lowerthan that of the opening or passageway ,81 and higher than that of theoor portion or bottom |92 of -t-he casing In this manner a chamberedstructure is provided wherein any gas sucked therethrough is rdrled orfreed ci -liquid or solid particles which may have :been entrained or intransit therewith.

A wet vacuum pump 1.93 is connected by suction piping |98 controlled bystop valve |85 to the hollow casing |88 in amanner whereby it is indirect communication with Athat upper portion of the -`chamber thereinwhich is at vthe side of the baille opposite the :passageway or intakeopening |81 leading tozthe chamber. A descending pipe It@ leads Afromthe discharge side of the pump. The lower end of :this descending pipeI9@ dips into apool of-'sealing liquid |81 that is preferablyvmaintained in a low box |83 having an `overflow weir |99 past whichthere is a release of overflow liquid lfrom the box |98 into thecompartment 88 and therefrom through the discharge opening 118|. The.barometric leg or scum conduit-l i4 is connectedtoithehollow casing andleads downwardly from the lower .portion of the separating chamber orlcasing' |88. The lbarometric leg I I4 is provided with a stop valve |65which can be opened or closed at will or even adjusted-to a partiallyopen position at the will of an operator. The valve H15 can Vhe leftopen and the valve I5 closed and in that instance the scum dischargeconstruction will function exactly'the saine as the scum discharge legIII of the form previously described.

It is feasible, however, in connection with the apparatus just referredto to omit the operation of pump I I 8 or even to operate it at a ratesomewhat less than that required to maintain the vacuum or desiredreduced pressure conditions for the gas in the tank I and in suchinstance in order to take care of the vacuum requirements the wet vacuumpump |93 is brought into operation. In such instance if the valve 5&5 isopen the scum which embodies some liquid will be sucked into the hollowcasing i88 with the gas. Therein the scum and gas directly contact thebaiiie I 9 I and this causes much of the liquid and entrained solids todrop into the lower portion of the casing while the gas continues on itswayto the pump |93. In this way the entrained liquid or solids, or amajor portion thereof, will enter the harornetric leg Ile, pass thevalve ii thereof and finally descend therethrough and from the leg iifiinto the low release box i I5. The gas and such scum as may continueentrained therewith will pass into the pump |33 and will thereby bedelivered into and ultimately from the descending pipe either into thebox |88, or for example, to and 11 through a valve-controlled dischargepipe |06. Mention has heretofore been made that the scum'weir ISW asprovided by the member |83 is vertically adjustable. This isaccomplished through the medium of a spider |68 which is carried at thelower end of a vertically-adjustable rod or stem |69. This rod passesthrough a sealing means |10 having packing |1| engaging the rod. Theupper end of the rod |66 is provided with screw threads |12 that areengaged by a hand-wheel or adjusting nut |13 which is suitably supportedfrom the cap member |84 through the medium of bracket member |14. Aninspection glass is provided at the top of the tank by the windowstructure |15. Means for illuminating the interior of the tank may beprovided by a member having an electric light As to the outow mechanismfor the clarified liquid, it will be noted that the rising members orupflow pipes 2| thereof extend to and terminate at the lower end of theauxiliary tank or compartment structure ||6, namely, in the compartmentor section |21 hereinafter referred to. This tank or compartmentstructure ||6 has a partition |25 that includes a vertically-adjustableoverflow member or dam |26, that provides the high liquid-fractionoverow weir ILO. The partition thus provided divides the lower interiorportion of the chamber of the auxiliary tank ||6 into a section |21 forreceiving the liquid upflowing into the chamber, and a section |28 forreceiving the liquid after it has overowed the weir member |26. From thecompartment or receiving space |28 the overowed liquid passes into andthrough the depending barometric leg section |23 and therefrom into thepool of liquid in the low release box or eiiiuent receiver |24.

The means for adjusting the weir or effluent overflow dam |26 is similarto that described in connection with the adjustable gates heretoforereferred to or the adjustable weir member |83 providing the scumtransfer edge SW of this form.

Apparatus of Figs. 7 to 12 inclusive The form of apparatus of Figs. '7,8 and 9 em- Ibodies the fundamental features of constructionspecifically described with respect to the first form shown in Figs. 1,2 and 3. It also embodies certain details of construction quite similarto those shown in connection with the second form shown in Figs. 4, and6. In addition, this third form has certain features or details ofconstruction peculiar to itself. This third form of apparatus is of atype which is peculiarly adaptable to divide liquid suspension havingsettleable solids therein into three fractions, namely, such as may beconsidered (l) a froth or scum-fraction, sometimes referred to as afloat-fraction; (2) a liquidfraction from which suspended solids havebeen floated and from which heavier solids have been settled wherebythere is left the liquid freed of such solids, namely, a fraction whichis generally referred to as the clarified liquid-fraction; and (3) afraction essentially containing heavy solids which readily deposit assediment at the bottom of the separation tank and which areprogressively removed therefrom as a settled-solids fraction.

In this form of apparatus the incoming suspension is conducted from thereceiving and treating basin 2||l into the draft tube or pipe 2|2 whichhas a horizontally-extending intake section 260, a curved intermediatesection 26| leading to an enlarged elbow section 268 from which thererises the upow section 262 that terminates as the expanding throat 26%by which the incoming feed is submergedly delivered within theliquid-holding portion of the tank, namely, at an elevation somewhatlower than that of the overflow weir ZSW but substantially higher thanthat of the lower edge 243 of the marginal wall 245.

The top of the tank 2|| as shown by Fig. 8 has an upwardly and inwardlysloping roof member 210 that provides a cylindrical upflow throatportion 21| which is concentric' with the marginal wall 245 and alsowith the upow section 262 and terminal throat portion 253 of the feedsupply pipe or draft tube 2|2. A vertically-adjustable ring-shapedmember 212 is arranged about the throat portion 21|. This member 2 12provides the scum overflow Weir ZSW and the adjustment thereof isattained through the medium of screw threaded rods 213 which arevertically positioned through the medium of suitably supportedhandwheels or nuts 214. As will be manifest from an inspection of Figs.8 or 13, the escape of gas past these rods 213 is prevented because ofthe packing and sealing construction provided at 215. The top portion ofthe tank is provided by a capping member 216, a downwardly and outwardlysloping member 211 and a downwardly and inwardly sloping portion 218. Asto the member 211 this, in horizontal section. is circular in plan andit is disposed so that it is concentric with the scum weir 2SW, or asotherwise expressed, with the ring member 212 providing said weir. As tothe member 218 this in horizontal section is circular in plan, but it islocated and disposed so that any such horizontal circular sectionthereof is eccentric with respect to the scum weir 212 whereby thereresults a scum launder or trough 2|3 which progressively increases indepth in passing towards the discharge section thereof which leads intothe barometric leg 2 |4. 'I'he members 216, 211 and v21|! are connectedso as to provide a gas-tight structure and the member 218 is in turnprovided with a gas-tight connection between it and the roof member 269.The packings 215 about the rods 213 are disposed in pockets provided onthe member 211 as is manifest from Figs. 8 and 13.

The means 220 for passing the clarified liquid from the lower orintermediate portion of the tank, to wit, from the bustle section 2|9embodies the upow conduits 22|, the auxiliary tank or chamber-providingstructure 2|6 and the downflow conduit or barometric leg 223. In theinstance of this structure, it will be noted that the upper ends of theupflow or rising conduits 22| are in alignment (see Fig. 7) andterminating in the lower portion of auxiliary tank 2|6 so as to deliverthe liquid into section 221 of the chamber 222 of that tank. The lowerportion of the chamber 222 is divided by the partition'225 andadjustable weir member 226 of that partition into said section 221 andsection 228, the latter of which is disposed for receiving overflowedclarified liquid passing thereto vfrom chamber 221 over the adjustablemember 226 or weir 2LO. The elevation of the weir 2LO, namely, of thehigh liquid-fraction overflow weir or effluent overflow dam as it isfrequently referred to is generally preferably lower, it may be onlyslightly lower, than the elevation of the scum Weir or overpass transferedge ZSW.

In this form of apparatus provision is made whereby there may be ensureda general elevation for the surface level of the liquid which is withina range between pre-determined maximum and minimum elevations. In orderto accomplish this, there is provided means for maintaining functionallyseparated from the scum, a relatively segregated small body of liquidwhich is in constant communication with the lower portion of the mainquantity of the liquid in liquidholding section of the tank. By way ofillustration such segregated liquid is shown as a body 280 which itsmaintainedin a space within a conning means 28 l. This body of liquid isin constant hydraulic communication with liquid in the lowerliquid-holding portion of the tank, as for example, by being establishedin communication with the liquid in bustle section 2|f9 through themedium of a pipe or other equivalent communicating member 282. The upperportion of the member 28| is in constant gas communication with theupper interior portion of the tank 2| I. This may be accomplishedthrough the medium of the pipe or communicating member 283, particularlyif the conning member 28| is located outside of the tank 2| There isarranged for use in conjunction with this segregated body of liquid 280a wet vacuum type of pumping means having two intake Vportionspreferably provided by adjustable intake nozzles, namely, a Wet pumpingmeans 219 having a lower intake means 284 provided with a loweradjustable intake nozzle 285 and an intake means 286 provided with anupper adjustable nozzle 281. The discharge from this pump is through themedium of a discharge leg 288 which is arranged to dip into a lowliquid-holding box 29| containing sealing liquid 292 for sealing thedischarge end of this pipe. The box 292 has an overow dam or releaseWeir 293 (see Fig. 7E) a section 296 for receiving overowed liquid, andan outow pipe 295. It is feasible, however, to eliminate the employmentof the discharge leg 288 as a barometric leg but in that case the pumpshould be of a type which would be able to discharge liquid therefromwithout permitting the back flow of air therethrough. Stop valves may beprovided at 296 and 291 respectively for the lower and upper suctionlines 28-4 and 286 of the pump.

As to the lower nozzle member 285, it is to be noted that this isadjusted in any suitable manner as by the handle 289 so that it canswing about a horizontally-extending axial bearing to raise or lower thefree or tip end of the nozzle member. It will also be noted that thisnozzle member and the pipe extending therefrom is constructed to providea downward passage no part of which rises above the intake end of thenozzle. In other words, any liquid entering the tip end of the nozzlewill necessarily gravitate towards the pump; such liquid does not haveto raise over a weir or any elevated point on its way to the pump. Onthe other hand, it will be noted that the upper nozzle 281 which isadjustable through the medium of the handle 290 is positionable so thatthe intake end or movable tip portion thereof swings up andd own and anyow of liquid or gas into that nozzle is raised from the elevationwhereat liquid is usually received thereinto whereby the liquidgenerally has some inward movement, due to an uplow passageway leadingfrom the intake tip of the nozzle prior to entry into the downflowportion of the upper suction line 268 In the normal operation of theapparatus the free end of the nozzle 285 of the lower suction line 284.is raised to a position higher than that of the overow weir 2LO; in someinstances, it maylbeiraised to-elevation'even higher than'that of thescum Weir A25W. The particular elevation employed is primarily dependentupon the type of incoming material supplied for treatment and thecharacter of material which has to pass the scum Weir ZSW. This vacuumpump 219 determines the vacuum or degree of reduced pressure Within theentire tank and associated system and in orer to prevent the existenceof too great a vacuum or too much reduced pressure within the system theupper nozzle 281 has been provided so as to commence to suck liquid andliquid only just so long as the elevation of the liquid in body 286exceeded or tended to exceed the elevation of the intake Section of thatnozzle 281. By the adjustment of these two nozzles one can substantiallycontrol the quantity flow of liquid into the tank 2| or as otherwiseexpressed, the height of the liquid in the tank whereby the quantity ofoutflow over the weirs will be under the control of that liquid which isthus adjusted as to height by the associated nozzles 265 and 281.

A mechanical raking mechanism has been provided for the tank 2| Thisv isembodied by a suitably driven and suitably supportedhorizontally-turntable bearing member 266 which is carried on astationary bearing member 26 The A turnable bearing member 260 carries avertical shaft 262 which extends downwardly through a sealingconstruction 244 on the member 216, downwardly through the upflo-wsection 262 and the enlarged elbow portion 268 of the draft tube M2 to alocality Within the lower region of the tank 2|| whereat it supports arake-carrying member 229 comprising outwardly-extending arms 246 fromwhich depend sediment-engaging and conveying means 341 provided by achain disposed for engaging sedimented material that is lodged upon thefloor provided by the tank bottom 25|.

Sedimented material is passed from the lower portion of the tank 2||through the valve-controlled conduit 252. In the instance of thisconstruction this conduit has two valves or gates embodied therein,namely, an upper valve or gate 261 and a lower valve or gate 269.Normally the upper valve is closed and the lower one is open.Immediately below the lower valve 269 there is a closed chamberstructure 263 having an open top body member 294 and a top member 265.In the chamber of this structure there is a sands-transfer valve orwheel 266 having sandsreceiving pocket portions or openings 261 therein.This sands-transfer wheel is horizontally turned through the medium of avertically-extending shaft 268 and speed reducing and power transmissionmechanism 264 driven from the rotor 295 of motor 266. Sands passing tothis wheel 266 are received in the successive pockets or openings andare transferred by the wheel to a locality whereat it is delivered orpassed into a transfer conduit 296 from which it is clischarged into areceiving chamber or tank 299 from which the sand is conveyed to alocality from the apparatus by means of a sprocket, chain and iiightconveying mechanism indicated at 249. In order that there may be avoidedany undue downward pressure on the sand wheel, it is feasible to makethis tank or receptacle 299 relatively deep so as to hold water thereinof sufficient depth to provide substantial counter-balancing pressureoperative against the underside of this wheel 266. If for any reason itis desired to empty the tank 2|| this can be readily accomplished evenwhen the lower valve or gate 269 is closed merely by opening the uppervalve 261. When the downward passage of sand through the conduit 252 isprevented by the closing of the lower gate or valve 259 one is enabledto obtain access to the sands transfer wheel 206 should occasionrequire.

There may be instances where it is advisable to inject gas or liquidinto the elbow section of the draft tube, namely, in the form of jetswhich extend into the elbow section and which are upwardly directedtowards and into the upflow section 252; such mode of injection isin-dicated in Fig. 12 by nozzle type of injector head 253. The liquid orair passed to this head 253 is supplied as through the medium of a pipe254 which is on the delivery side of a pump 255 the latter of which hasa valve-controlled air suction line 250 leading from the upper interiorportion of the tank 2l l and a valve-controlled water suction line 251leading for example from the liquidholding compartment 221 wherebyclarified liquid from the tank may be returned for any purpose desiredinto and through the injector or distributor head 253.

It will also be noted in this connection that any pumping of air orother gas from the upper interior portion of the tank back into the tankor any pumping of liquid from any portion of the unit back into the tankdoes not change or alter the reduced pressure conditions of the gaswithin the tank or height of liquid within the tank. There are instanceswhere it may be advisable to inject air into the froth or floatingmaterial in the upper portion of the tank in order to function as ameans for impelling the floating material towards and past the scumoverflow Weir or float-transfer edge ZSW. Such a means is indicated invertical section by Fig. 13 and in plan by Fig. 14.

Respecting Figs. 13 and 14 In these figures the distributing head forthe air is indicated by 300; the jets of air 30| delivered therefromhave a tangential arrangement or disposition as is clear from Fig. 14whereby they tend to impart a slight swirling and progressive outwardmovement on the oat material towards the scum overow weir 2SW, and thusaid in eiecting the passing of the floating material past the weirWithout compelling the possible employment of an undue amount ofove-rilow liquid to accomplish that purpose. The gas employed for thispurpose is preferably some of the reduced pressure air or other gaswhich is sucked from the upper interior portion of the tank 2H into thepump 302 through the suction line 353 indicated in Fig. 13 and deliveredthrough the line 304 into the distributing head 300. Figs. 13 and 14 areindicative of a type of construction which can be used in connectionWith the tank 2l I and particularly in connection with the form ofapparatus shown in Fig. 8. Figs. 13 and 14 should be therefore viewed asdetails of construction Wlu'ch are used in and as part of the form ofconstruction shown in Fig. 1l.

Respecting Fig. 15

In Fig. 15 there is illustrated a modified form of adjustable scumoverflow weir which is herein designated as 342 as it may be substitutedin place of the scum overflow Weir 212 shown in Fig. 8. The type ofoverflow Weir just referred to leads to a steady and easy transfer offroth material by avoiding a sharp edge or ledge over which the floatingmaterial must pass on its way into the scum launder I3.

Cil

Further respecting Figs. 7 to 12 inclusive Reference is now made to theconstruction of the draft tube 212 and the associated baffle ordistributing means at the terminal thereof as shown in Fig. 8. Here itwill be noted that instead of employing a flat distributing disc as isthe situation in the instance of two forms previously described, thereis a downwardly and outwardly sloping member 250 and there is a passagearea 258 between the upper surface and outer edge of this member 250 andthe inner contour of the top member 210 of the tank. The upper surfaceof this member 250 follows the contour of a frustrum of a cone andensures suicient retention thereover of the liquid-solids suspensionwhereby it continues under the relatively direct or most powerfuliniluence of the reduced pressure existing within the upper portion ofthe tank. Because of its shape the distributing member 250 provides forthe gradual downward slipping of any settable solids which are notsusceptible to the influence of the reduced pressure of the air withinthe tank. Immediately below this distributing member 250 there is adownwardly and inwardly extending member 259 which permits an easy,gradual and relatively unobstructed rising of any material tending torise from the region immediately below it, particularly of any materialtending to move upwardly because of the reduced pressure conditionsmaintained within the tank. This member 259 also serves as a means bywhich the inner or upper end section of the draft tube derives supportfrom the marginal wall 245 through the medium of the members or brackets359.

With respect to the liquid-height control as realized by the adjustablenozzles 285 and 281, it will be noted that these nozzles and the pumpingstructure associated therewith can be lo cated anywhere with respect tothe apparatus whereby it can engage and control a segregated portion ofthe body of liquid within the tank that is preferably separated orbailled from the scum within the tank whereby clear liquid relativelyfree of oating material will come under the inuence of these nozzles. Aprime purpose of these nozzles is to maintain and establish minimum andmaximum level elevations within relatively ne Aand carefully selectedlimits. For this purpose these nozzles could therefore be placeddirectly within the main tank itself or within the liquid-holdingportion of the auxiliary tank structure 2|6, or as otherwise expressed,they do not have to be embodied in and as part of an outside structureor chamber.

General In each of the forms shown the incoming liquid suspension istreated as by the dispersion of air, and other material, and throughoutthe same, namely by the air distributing and dispersing means employingthe impeller 34, |34 or 234. Such treated liquid suspension ispreferably held just long enough within the treating station or basinl0, H0 or 2li) to permit the escape of large gas bubbles but wherebyth'e small dispersed gas bubbles will continue therein. The pre-treatedliquid suspension is conducted through the draft tube and is therebysubmergedly delivered upwardly into the body of liquid or liquidsuspension maintained within the separating chamber. In this chamberunder the influence of the reduced pressure gas therein there iseffected a rising of the float material as. froth, scum, or otherW-f'trough, scum transfer means for passing scum floating material to thetop of the liquid within the tank. The collecting floating materialpasses the overpass transfer edge of overflow Weir SW, ISW or 2SW.thence into the scum launder i3, l i3 or 2 i3 from which it is deliveredto a locality outside of the tank without permitting the ingress of airinto the tank Il, Ill or 2li, as the case may be, namely. throughsuitable discharge means such is provided by the barometrlc leg.construction M, il@ or 2M. Clarified liquid from a lower or intermediateportion of the tank, to wit, from a bustle section I8, H8 or 219thereof, passes through the upflow conduits 2 l, 121 or 221, past thehigh liquid-fraction overflow weir or eiuent overflow dam LO, ILO or BLOfrom which it is delivered as overow eiuent into a region from which itpasses through a barometric lee,l construction or other equivalent meansto the exterior of the unit without permitting the entrance of air intothe tank. In the form shown in Fig. 8 there is provided means whereby athree-way of fraction split can be carried out to obtain a froth orneat-fraction, a clarified liquid-fraction, and sedimentedsolids-fraction.

Suitable window structures each having a transparent medium as glass isprovided as at C, CC or CCC whereby the interior conditions within theupper portion of the unit can be observed, particularly as to the overowconditions for the scum in the region of the scum weir, or for theoutflowing liquid in the region of the liquidfraction overflow weir.

These windows may be located and availed of for observing operatingconditions in any part of the structures. The window structures arepreferably large enough to serve as manholes or access openings. Suchwindow structures are normally closed and the access openings providedthereby are indicated in the different forms, namely, by referencecharacters C, CC or CCC.

Novel features of construction revolve about the mode in which thedifferent parts of the tank and its associated features are brought intocooperative organization and arrangement. Novel features of theconstruction described are set forth and are more particularly definedin and by the claims hereof.

This application is a continuation of and a full substitute for and inplace of parent application Serial No. 436.972, led February 14, 1942.

What is claimed is:

l. Apparatus comprising a closed tank adapted to hold an ever-changingbody of liquid suspension being treated; an auxiliary chamber adapted tohold liquid with a space for a gas atmosphere overlying and contactingthe liquid; eliluent-o-utflow means including a dam having within saidchamber an overflow edge lower than that of the uppermost interiorportion of the tank and chamber whereby normally to determine thesurface level of the body of liquid in the tank sufficiently low toprovide therein space for a gas atmosphere overlying and contacting theliquid body; feeding means for delivering feed liquid submergedly to theliquid body and having a discharge terminal at an elevation lower thanthat of the overflow edge of said dam; means normally sealing saidfeeding means against leakage of outside air thereinto and thence intothe tank; scum removal means for withdrawing scum floating on the bodyincluding an open top trough having an overpass edge at an elevationapproximate that of the overflow elevation of said dam for receivingfloating scum passing over said edge into the from the trough to aregion outside oi' the tank and means for minimizing leakage of outsideair into and through said scum transfer means; means for providing gascommunicating passage area between the Aspaces for gas overlying theliquid in the tank and the liquid in the chamber; and means for suckinggas from at least one of said spaces for subjecting liquid underlyingthe gaswithin both spaces to sub-atmospheric pressure; saideflluent-outow means having its dam operatively disposed with respect tothe chamber and` including an intake section for receiving liquidpassing thereinto from a region within the tank which is at elevationvlower than that whereat feed liquid is submergedly delivered into the'tank from the discharge terminal of the feeding means, a conduit leadingfrom the intake section to the chamber whereby tol realize a column ofupflowing eflluent which must pass as overflow from said dam, aneffluent receiver for retaining a quantity` of effluent asa. sealingmedium, and an overflowed-elliuent conduit extending downwardly fromaportion of the chamber at the delivery side ofthe dam anddipping in thesealing medium for providing a barometric leg.

2. Apparatus according to claim l, in which thedam is located within theauxiliary chamber, and in whichv the overpass edge of the scum troughextends horizontally and is csposed at anelevation somewhat higher thanthat of the overflow edge of the dam.

-3. Apparatus according to claim l, with the addition of means foreffecting relative vertical adjustment as between the overpass edge ofthe scum troughv on the one hand and the overo-w edge of the dam on theother hand.

4. Apparatus according to claim l, having means positionable fromoutside of the apparatus for effecting relative vertical adjustment asbetween the overpass edge of the trough on the one hand and the overowedge of the dam on the other hand.

5. Apparatus according to claim 1, wherein the dam has means extendingfrom it to a place of atmospheric pressure whereby to adjust theelevation of the overflow edge of the dam and thereby the overflowelevation of liquid in transit through the auxiliary chamber therebycontrolling the level of the liquid within the tank.

6. Apparatus according to claim 1, wherein the tank has at the lowerportion thereof an ellluen-t collecting section annular in planproviding the intake section of the eilluent outflow means and whereinthe eiliuent outflow means comprises a plurality of up-flow pipes eachconstituting a conduit leading to the chamber from the thus provided.inlet section and as to which pipes the lower intake ends thereof aresymmetrically spaced and are in communication with said collectingsection while the upper ends extend into the auxiliary chamber wherebyto provide individual ellluent overflow members that collectivelyfunction as the overflow dam.

i. Apparatus for performingr a continuous process for separating andremoving suspended matter as scum from a liquid suspension, whichcomprises a closed tank. providing a liquid-holding portion for thedetention therein of an everchanging body of such suspension having aliquid level normally maintained up to a minimum elevation and providingan upper interio-r portion affording a gas-confining space wherein thereexistsv a gaseous medium at sub-atmospheric pressure that contacts saidbody; a closed auxil- 19 lary chamber providing a liquid-receivingportion and an overlying interior portion aording a gas-confining space;means defining a communicating gas passageway between said gas-confiningspaces whereby the sub-atmospheric pressure conditions therein continuesubstantially alike; outflow-conduit means having a low intake forreceiving liquid from the ever-changing body within the tank and leadingupwardly to the auxiliary chamber for holding a column of upowingeffluent; effluent overflow dam disposed within the auxiliary chamberand having an overflow elevation lower than that of the top interior ofthe closed tank for determining said minimum elevation for the liquidlevel in the tank; gasexhausting means operatively connected to theupper interior portion of the apparatus for removing gas from saidgas-confining spaces whereby sub-atmospheric pressure is maintainedtherein; suspension feed means having a discharge terminal at elevationhigher than that of the intake of the outflow conduit means but lowerthan that of the overflow edge of the dam for submergedly deliveringsuch suspension as feed material into said tank; means for normally ysealing against leakage of outside air into and through said feed meansand thence into the tank; an effluent receiver for retaining a quantityof the effluent as a liquid sealing medium; conduit means providing abarometric leg for conducting overowed effluent from the auxiliarychamber downwardly into the receiver and dipping into the sealing liquidtherein; a scum trough located in the upper interior portion of the tankand having an overpass edge at elevation approximate that of theoverflow edge of said dam; means for discharging scum from said troughto the exterior of the apparatus and means for minimizing leakage ofoutside air into and through said last mentioned means and thence intothe tank.

8. A unit of the class described comprising in operative combination andarrangement a gastight tank; a gas-tight auxiliary chamber, meansproviding gas communication between the upper portion of the tank andthe upper portion of the chamber; upflow conduit means leading from alower portion of the tank into the lower portion of the chamber; aneffluent receiver exposed to the atmosphere for receiving liquiddischarged thereinto and having a release weir for retaining liquid inthe receiver up to the elevation of the weir; a conduit providing abarometric leg extending from the lower portion of the chamberdownwardly into said effluent receiver and terminating at elevationlower than that of said release Weir; an eiiiuent overflow damoperatively disposed with respect to the chamber and having an overflowedge over which liquid in transit to and through said chamber must passbefore entering said downow conduit, the elevation of which overflowedge is lower than that of the uppermost interior portion of the tank; afeedsupply basin for holding the material to be treated in a mannerwhereby said material is exposed to the atmosphere; feeding meansincluding a draft tube for transferring feed material from said basininto the tank at an elevation lower than that of the overow edge of saiddam but higher than that of the intake section of said upiiow conduitmeans; a scum collector exposed to the atmosphere for collecting scumdischarged thereinto, a scum outflow weir for the collector forretaining in the scum collector scum and liquid thereof up to theelevation of the scum Weir; a scum-receiving hopper within said tankhaving an overpass edge at an elevation higher than that of the overowedge of said dam but of sufficiently low elevation for permittingpassage thereover of quantities of scum floating on the liquid bodywithin the tank; a closed conduit providing a barometric leg extendingfrom a portion of said hopper downwardly into the scum collector andterminating at an elevation lower than i that of the scum outfiow weir;and pumping means connected for withdrawing quantities of gas from thegas-communicating upper portions of the tank and chamber whereby thepressure of gas remaining therein is sub-atmospheric.

9. A unit of the class described for functioning in association with afeed supply basin for holding a supply of liquid suspension, with aneliluent receiver having a release weir determining the minimum depth ofthe eiiluent retained in the receiver, and with a scum collector havinga scum outflow weir determining the minimum depth of released liquidpassing with scum into said collector; and which unit comprises a closedtop main tank for holding within the lower portion thereof anever-changing liquid body of supplied suspension fed thereinto andWithin the upper portion thereof a gaseous medium at sub-atmosphericpressure to which said body is directly exposed; barometric leg meansfor discharging effluent therethrough including an auxiliarycompartment, an overflow dam functionally dividing the interior of theauxiliary compartment intoY pool retaining portion and overlowedliquid-receiving portion, a conduit section for upflowing effluentleading from a liquid-holding portion of the main tank upwardly to saidpool portion, and a conduit section for gravitating effluent leadingdownwardly from said ove-rowed liquid-receiving portion into theeliiuent receiver for providing a barometric leg terminating therein atelevation lower than that of the release weir thereof, the overflowelevation of said dam being lower than that of the uppermost interiorportion of the closed top of the main tank but higher than that of theintake portion of said upowing effluent conduit section therebydetermining a minimum normal liquid-level of the liquid within the tank,and the auxiliary compartment having within the upper portion thereof agas-holding space extending to elevation substantially above that of theoverflow elevation of said dam; means providing a passageway between thegas-holding spaces of the tank and of the compartment whereby the samesub-atmospheric pressure is realized in said spaces; pumping meansconnected and disposed for withdrawing quantities of gaseous medium fromsaid passageway connected gas-holding spaces within the tank and Chamberfor maintaining the pressure therein sub-atmospheric; feed-conductingmeans comprising transfer piping having a continuously submerged intakeleading from the liquid-holding section of said feed supply basin andterminating within the main tank at elevation lower than that of theoverflow elevation of said dam but at elevation higher than that of theintake portion of said uplowing efliuent conduit section; and a scumtrough within the tank having an overpass edge at elevation approximateto but somewhat higher than that of the overflow edge of said dam andhaving a downflow tubular section providing a barometric leg leadingfrom said trough into the scum collector and terminating therein atelevation lower than that of the scum outflow weir thereof.

10. Apparatus comprising a closed tank to hold an ever-changing body ofliquid the surface of which is directly exposed to overlying gases,means for sucking gas from the upper portion of the tank for effectingsub-atmospheric pressure on said gases, means for submergedly deliveringgasbearing liquidsuspension into said body of liquid, a scum trough opento the gases in the tank, an overpass transfer edge for said trough atelevation lower than that of the top of the tank but higher than that atwhich the suspension is delivered and over which transfer edge scumfloating at the top of said body must pass before being received intosaid trough, means for discharging scum from said trough to a localityoutside of the apparatus, means cooperatively associated with the latterfor minimizing leakage of outside air thereinto, eliiuent outflow meanscomprising a bustle section constituted as hereinafter described forconducting liquid from the interior of the tank to a region outside ofthe apparatus and means cooperatively associated with the effluent outowmeans for minimizing the leakage of outside air thereinto; said tankhaving an upwardly extending marginal wall, roof means connected to saidwall, an annular member providing the top of the bustle section theinterior edge of which is connected to said wall at elevation higherthan that of the lower edge of the wall whereby the lower end portion ofthe wall provides an inner wall member of the bustle section, anoutlying ring connected to the outer portion of said annular member andextending downwardly there from providing a peripheral member of saidbustle section, and a bottom member connected to the lower edge of saidring for completing the lower limits of the bustle section whileproviding for the tank a floor which is vertically spaced below thelower edge of the marginal wall whereby a constantly open efiluentpassageway is provided leading into the bustle section, the latter ofwhich provides the eiuent intake portion of the aforementioned eluentoutflow means.

l1. Apparatus of the class described comprising in combination asubstantially closed tank embodying a ,marginal wall, a roof portionconnected to said marginal wall and providing a gasreceiving spacewithin the upper interior portion of the tank, an annular memberproviding the top of a bustle section whose inner edge is connected tosaid marginal wall at an elevation somewhat higher than that of thelower edge of the marginal wall, a peripheral member connected to theouter portion of said annular member and extending downwardly therefrom,a tank bottom connected to the lower portion of said peripheral memberbut vertically spaced below the lower end of said marginal wall toprovide a substantially open passageway between them, and a scum troughwithin the tank having an upper margin thereof providing an overpassedge at an elevation substantially lower than that of the upper interiorof the roof portion but at elevation substantially higher than that ofthe lower end of the marginal wall and over which transfer edge scumwithin the tank must pass before entering said trough; said bustlesection being provided by said lower portion of the marginal wall, saidannular member, said peripheral member extending downwardly from saidannular member and a portion of said tank bottom; an auxiliary chamberassociated with the tank having a liquidholding section and an overlyinggas-receiving space; means providing constant communication between theoverlying gas-receiving space of the auxiliary chamber and thegas-receiving space within the upper portion of the tank; conduit meansleading upwardly from the bustle section and delivering liquid into saidchamber; means providing an effluent overflow dam within said chamberhaving an overflow edge at an elevation substantially higher than thatof the lower end of the marginal wall and slightly lower than that ofthe overpass edge; means for conducting overflowed liquid from saidchamber to a locality outside of the tank and associated therewith meansfor minimizing inflow therethrough of outside air; means for conductingscum from within said trough to a locality outside of the tank andassociated therewith means for minimizing inflow therethrough of outsideair; pump means for withdrawing gas from within the gas holding spacesof said tank and chamber; and means for feeding liquid-suspension to theinterior of the tank while minimizing inflow of outside air fordelivering such fed material into a region of the tank which is atelevation somewhat lower than that of the elevation of the overflow edgeof said dam but substantially higher than that of the lower end of themargin wall of the tank.

12. Apparatus comprising a closed tank to hold an everchanging body ofliquid the surface of which is directly exposed to overlying gases,means for sucking gas from the upper portion of the tank for effectingand maintaining a sufiiciently low subatmospheric pressure on said gaseswhereby the surface level of the everchanging body will be at elevationsufficiently high for floating scum to be passed from the body over thehereinafter referred to transfer edge into the trough also hereinafterreferred to; means for submergedly delivering gas-bearing liquidsuspension into said body and means associated therewith for minimizingthe leakage of air thereinto; means for conducting effluent from a lowerportion of the tank to a locality outside of the apparatus and meansassociated therewith for minimizing leakage of air thereinto; and scumdischarge means for receiving floating scum from the body of liquidwithin the tank and for delivering the scum to a locality outside of theapparatus and means associated therewith for minimizing leakage of airthereinto; said tank having an upwardly extending marginal wall, bottommeans connected to the lower portion of said wall, a frustro-conicalroof member of which the small upper end is open while the outer portionof the larger lower end is connected to the upper portion of themarginal wall, means along the upper end of said roof member forproviding a transfer edge circular in plan over which passes floatingscum from within the upper end of said roof member, and an invertedcup-shaped capping member for completing a closure top for the tank,said capping member being disposed so that the top thereof is verticallyspaced above said transfer edge and has a downwardly extending wallportion thereof circular in plan and eccentrically disposed with respectto said transfer edge as well as horizontally spaced about said transferedge and extending downwardly to the frustro-conical roof member toprovide with the latter a trough of progressively increasing depth forreceiving scum passing said transfer edge, which said scum dischargemeans comprises the thus defined trough and also includes conduit meansextending outwardly from the deep section of the trough.

13. Apparatus comprising a closed tank adapted to l,hold anever-changing body of liquid suspension being treated; means fordelivering feed 23 liquid into said body; effluent-outflow meansincluding a dam for controlling the liquid level in the tank to providespace for a gaseous medium overlying the liquid body into which thelatter is directly exposed; an auxiliary chamber adapted lto hold liquidwith a space for gaseous medium overlying and directly contacting liquidtherein; means providing communication between said spaces; means forsucking gaseous medium from at least one of said spaces for subjectinggaseous medium in said spaces to sub-atmospheric pressure; saideiiluent-outflow means including a conduit leading from a region in theliquid-holding portion of the tank at elevation lower than that whereatthe feed liquid is delivered into everchanging body and extendingupwardly to the auxiliary chamber thereby providing means for holding acolumn of upflowing eiiluent enroute to the auxiliary chamber, eiuentreceiver for retaining a quantity of eiiluent as a sealing medium and anoverflowed eflluent conduit extending downwardly from the chamber anddipping into the sealing medium serving as a barometric leg; said tankhaving an upwardly extending marginal wall, a bottom member connected tothe 'lower portion of said wall, a frustro-conical roof member of whichthe smaller upper end is open providing a throat portion while the outerportion of the larger lower end is connected to the upper portion of themarginal wall, means along the upper end of said roof member embodying avertically operable throat adjusting member providing a transfer edgeover which there passes floating scum from within the throat portion, aninverted cup-shaped capping member for completing the.closure top of thetank so disposed that the top thereof is vertically spaced above saidtransfer edge and having wall portion surrounding but horizontallyspaced from said transfer edge while extending downwardly to thefrustro-conical roof member to provide with the latter a trough forreceiving scum passing said transfer edge; a scum collector for holdingsealing liquid therein; and conduit means leading from the trough andserving as a barometric leg extending into the liquid within saidcollector.

la. Apparatus according to claim 13, having means connected to saidthroat-adjusting member and extending into the atmosphere outside ofsaid apparatus for vertically positioning said throat member.

l5. An apparatus for performing a continuous process for separating andremoving floatable matter as scum from a liquid suspension, whichcomprises in operative combination a closed. tank providing therein alower liquidholding portion wherein there is established a body of suchsuspension and also providing therein an upper gas-holding space inwhich the gas directly overlies said body; a closed auxiliary chamber; aclosed secondary chamber; Vsaid auxiliary chamber providing alower-liquid-receiving portion for liquid passed thereinto from a columnof upowing eiiiuent and an upper gas-holding space wherein gas directlyoverlies liquid within the lower portion thereof; said secondary chamberproviding a lower liquidholding portion and an overlying gas-holdingspace; gas-communicating means between the gas-holding spaces of saidtank and chambers whereby the pressure of the gas therein is equalized;feeding means for delivering as feed material the liquid suspension tobe treated in said main tank; means associated with said feeding meansfor minimizing leakage of Voutside air into the feed means and thenceinto the tank; upow-conduit means leading from a low region of theliquid-holding portion of the tank to the liquid-holding portion of saidauxiliary chamber, which said lower region is at elevation lower thanthat at which the feed material is delivered into the main tank;eiiuent-overilow dam means within said auxiliary chamber over whicheffluent passing in transity through the auxiliary chamber must overflowwhereby the normalminimum level of the liquid body within said tank ismaintained substantially up to an overflow elevation of saideuent-overlow dam means; tubular means for passing overflowed liquidfrom the auxiliary chamber to the exterior thereof; means associatedwith said tubular ymeans for minimizing leakage of outside air into thetubular means and thence into the auxiliary chamber; means providing apassageway between the liquidholding portion of the tank and theliquid-holding portion of the secondary chamber whereby the tank and thesecondary chamber are in constant hydraulic communication; pumping meansfor sucking gas from said gas-holding spaces for thereby maintaining thegas therein at pressure substantially sub-atmospheric, said pumpingmeans comprising intake suction piping having suction nozzle meansproviding an intake tip operatively disposed within the secondarychamber and positioned for receiving liquid preparatory to passingliquid through the nozzle means when the level of the liquid within thesecondary chamber rises to exceed the elevation of said suction nozzlemeans whereby said pumping means functions to remove by suction liquidentering said nozzle means; a scum trough within the tank having anover-pass edge at elevation approximatelyV that of the overflowelevation on said dam and over which edge scum floating within the tankmust pass into the trough preparatory to delivery therefrom to a regionoutside of thetank; scum-discharge means for passing such transferredscum from the trough to the exterior of the tank; and means associatedwith the scum-discharge means for minimizing leakage of outside air intothe tank.

16. Apparatus comprising l a closed tank wherein there is normallymaintained an everchanging body of liquid directly exposed, to anoverlying gaseous medium; pumping means for sucking gaseous medium fromthe apparatus for `maintaining gaseous medium remaining in the apparatusat sub-atmospheric pressure; feed supply means having a dischargesection delivering gas-bearing liquid suspension containing oatablematter into the tank at an elevation intermediate the top and bottom ofthe tank and means for minimizing air leakage into said feed supplymeans; a trough open to the gaseous medium within the tank, an over passedge for the trough at elevation higher than said feed dischargeelevation but lower than the the top of the tank over which overpassedge fioating material from the said body passes before being receivedin said trough; discharge means for passing floating material from saidtrough to outside the apparatus and means for minimizing air leakageinto said discharge means; and efluent-outow means'leadign from theinterior portion of the tank at elevation lower than said feed dischargeelevation to outside the apparatus and means for minimizing air leakageinto said effluent-outflow means; said apparatus being characterized inthat there is a pumping meanschaving a gas suction line connected to andin communication with the interior of the upper gaseous medium holdingportion of the apparatus, and a discharge line embodying agas-distributing member having discharge orifices for delivering pumpedgaseous medium as jets directed to impel the floating material over saidedge.`

17. Apparatus comprising a closed tank wherein there is normallymaintained an everchanging body of liquid directly exposed to overlyinggas conned within the upper interior portion of the apparatus; pumpingmeans for sucking gas from withinthe upper portion of the apparatus formaintaing gas remaining therein at sub-atmospheric pressure; feed-Isupply means having a discharge section delivering gas-bearing liquidsuspension containing iloatable matter into the tank at an elevationintermediate the top and bottom of the tank and means for minimizing airleakage into said feed supply means; a trough open to the subatmosphericgas within the apparatus, an over-pass for the trough edge at elevationhigher than said feed dischargeelevation but lower than the top ofthetank and over which edge floating material on said body must pass beforebeing received in said trough; discharge means for transferring floatingmaterial from said trough to outside the apparatus and means forminimizing air leakage into said discharge means; an efiiuent-outowmeans leading from an elevation within the tank lower than that of saidedge to outside the apparatus and means for minimizing air leakage intosaid eiiluentoutflow means; said apparatus being characterized in thatit includes pumping means having a gas suction line for conductingsucked gas from the upper interior portion of the appa-` ratus, and adischarge line having a terminal portion providing discharge openingslocated at elevation lower 'than that of the over-pass edge of thetrough and delivering the pumped gas upwardly and outwardly into oatingmaterial within the tank for impelling the floating material over theover-pass'edge.

18. Apparatus comprising a closed tank wherein there is normallymaintained an ever-changing body of liquid directly exposed to anoverlying gas; pumping means for sucking gas from the apparatus formaintaining gas remaining in the tank at sub-atmospheric pressure; atro-ugh open to the gas within the tank. an over-pass edge for thetrough elevation intermediate that of the top and bottom of the tank andover which edge oating material on said body must pass before receipt insaid trough; discharge means for passing iloating material from saidtrough to outside the apparatus and means for minimizing air leakageinto said discharge means; feed-supply means having a discharge sectionfor delivering gasbearing liquid suspension into the tank at anelevation lower than that of said edge and having means for minimizingair leakage thereinto; and effluent-outflow means leading yfrom aninterior portion of the tank but lower than that of said edge to outsidethe apparatus and having means for minimizing air leakage thereinto;said apilaratus being characterized in that it has pumping means havinga suction line leading from an upper interior region of the apparatusfor sucking sub-atmospheric pressure gas therefrom, and a discharge linefor delivering gas thus pumped into GVeT-p aSS 26 the liquid within thetank at elevation lower than that of the over-pass edge of the trough.

19. Apparatus comprising a closed tank wherein there is normallymaintained an ever-changing body of liquid directly exposed to overlyinggas; pumping means for sucking gas from the apparatus for maintaininggas remaining in the tank at sub-atmospheric pressure; a trough open tothe gas within the tank, an over-pass edge for the trough at elevationintermediate that of the top and bottom of the tank and over which edgefloating material on said body must'pass before receipt in said trough;discharge means for p-assing floating material from said trough tooutside the apparatus and means for minimizing air leakage into saiddischarge means; feed-supply means having a discharge Vterminal fordelivergas-bearing liquid suspension into the tank at an elevation lowerthan that of said edge and having means .for minimizing air leakage intosaid feed-supply means; means leading from an interior portion of thetank lower than that of said edge to outside the apparatus and havingmeans for minimizing air leakage into said eiiluent-outflow means; saidapparatus being characterized in that there is pumping means having asuction line leading thereto from an upper interior region of theapparatus for sucking sub-atmospheric pressure gas, and a discharge linefor delivering said gas thus pumped into the tank at elevation lowerthan that of said discharge terminal.

2). Apparatus comprising a closed tank wherein there is normallymaintained an ever-changing body or liquid directly exposed to anoverlying gas; pumping means for sucking gas from the 'apparatus formaintaining gas remaining in the elevation below that of the top of thetank but higher than that of said discharge terminal and over which edgeoating material on said bodyy must pass before receipt in said trough;discharge means for passing floating material from said trough tooutside the apparatus and means for minimizing air leakage into saiddischarge means; and eiiiuent-outilow means leading from an interiorportion of the tank lower than that of said edge to outside theapparatus and means for minimizing air leakage into said eiiuent-outowmeans; said apparatus being characterized in that there is pumping meanshaving a suction line leading from an interior portion of the apparatusbelow said feed discharge terminal for conveying sucked uidtherethrough, and a discharge line for delivering the thus sucked andpumped fluid Within the tank at elevation lower than that of andeffluent-outflow.

said feed-supply means; a trough open to the gaseous medium within thetank, an over-pass edge for the trough at elevation higher than saidfeed discharge elevation but lower thanthe top of the tank over whichedge floating material on said body must pass before receiptI in saidtrough; discharge means for passing floating material from said troughto outside the apparatus and means for minimizing air leakage into saiddischarge means; effluent-outflow means leading from the interiorportion of the tank at elevation lower than said feed dischargeelevation to outside the apparatus and means for minimizing air leakageinto said effluent-outflow means; said apparatus being characterized inthat it includes a pump having a suction line in and constituting partof liquid transfer means leading from a liquid-holding portion of thetank functionally disposed below the deliveryv of said feed-supplymeans, and a discharge line leading from the pump for directivelydelivering pumped liquid into said feed-supply means for furthering theforward passage of feed material upwardly from the same.

22. Apparatus of the class described comprising a closedrtank whereinthere is normally maintained an ever-changing body of liquid directlyexposed to overlying gaseous medium; pumping means for sucking gaseousmedium from the up per interior Vportion of the tank for maintaininggaseous medium remaining in the tank atoressures sub-atmospheric;feed-supply means having a tubular section affording an upow deliveryportion disposed for submergedly delivering gas-bearing liquidsuspensions containing floatable matter into the tank at a feeddischarge elevation intermediate the topand bottom of the tank and meansforl minimizing air-leakage into said feed-supply means; a trough opentothe gaseous medium within the tank, an over-pass edge for the troughat elevation higher than said feed-discharge elevation but lower thanthat of the top of the tank and over which transfer edge floatingmaterial on said body of liquid must pass before being received in saidtrough; transfer means for passing floating material from said trough tooutside the apparatus and means for minimizing air leakage into saidtransfer means; and effluent-discharge means leading from the interiorportion of the tank at elevation lower than said feed dischargeelevation to outside the apparatus and means for minimizing air leakageinto said effluent-discharge means; said apparatus being characterizedin that it includes pumping means for withdrawing sub-atmosphericpressure gaseous medium from within a gas-holding space of said tank, adischarge conduit leading from said pumping means, and a distributinghead in which said discharge conduit terminates, which head is arrangedin association with .a portion of said tubular feed section and hasdischarge openings for delivering pumped gaseous medium into the tubularsection for assisting the flow of feed material forwardly within thetubular section.V

2'3. Apparatus for performing a continuous process for separating andremoving suspended matter from a liquid-solids suspension, whichapparatus comprises a closed tank providing within the upper interiorportion thereof a sectionfor holding a gaseous medium at sub-atmosphericpressure and providing within the underlying interior portion thereof asection for holding an ever-changing body of such liquid undergoingtreatment thatV is constantly exposed to said overlying gaseousmedium;'a receiving trough, an over-pass edge for' the trough over whichiloating material'from the body of liquid underu going treatment mustpasspreparatory to being received into the trough and whose elevation issubstantially higher than that of the bottom of said tanky butsubstantially lower than that of the uppermost interior portion of thetop of the tank; a'basin outside of said tank for holding.

under atmospheric pressure conditions feedliquidcontainingsolids'suspended therein; adraft tube having an intake endsubmerged within the liquid within said basinarid a terminal dischargewithin but located above the bottom of the tank at elevation lower thanthatl of said over-pass the effluent within said receiver, `said eluentdam.

having an' overow elevation lower than that of the uppermostinterior'portion of thev compartment but proximate that of the over-passedge for the trough; a collectorlocated outside of the Atank for holdingtherein a maintained bodyof sealing liquid; conduit means providingabarcmetric leg .extending downwardly from said trough and into saidcollector so that thevdist, charge end thereof is constantly submergedin the ing body of such liquid undergoing treatment thatis constantlyexposed to said overlying lgaseous liquid within said collectorgmeansproviding constant gas communication between the upper in terior portionof the tank and the upper interior portion ofY the compartment; gaspumping means for removing gaseous medium from the upperinu teriorportions of the tankY and compartment and for vdischarging gaseousmedium pumped thereby to a locality outside of the tank, and secondpumping means providing` a suction passageway leading Yto the secondpump from the eiiuentM outflow means, and means providing a dischargepassageway leading from the second pump disposed for delivering pumpedfluid into a liquidholding portion of the tank. Y Y

' 24. An apparatus for performing a continuous process for separatingand removing suspended matter from a liquid suspension, which apparatuscomprises a closed tank providing within the upper interior portionthereof a section for holding a gaseous medium at subatinospheric pres-vsure and providing within a lower interior portion thereof a section forholding an ever-changmedium; a trough, an over-pass edge for the troughover which floating material from the body of liquid undergoingtreatment must pass preparatory to being received in the trough Whoseelevation is substantially higher than that of the bottom of the tankbut substantially lower than that of the uppermost interior portion ofthe top of the tank; a basin outside of said tank for holding underatmospheric pressure feed liquid containing solids suspended therein; adraft tube having a lower intake end submerged within the liquid in saidbasin and an upper discharge

